How do you define a GraphQL object type, enum, and union in code-first NestJS?

Q: How do you define a GraphQL object type, enum, and union in code-first NestJS?

// Object type @ObjectType() export class Post { @Field(() => ID) id: string; @Field() title: string; @Field({ nullable: true }) body?: string; @Field(() => [Tag]) tags: Tag[]; @Field(() => User) author: User; } // Enum — must be registered before use export enum PostStatus { DRAFT = 'DRAFT', PUBLISHED = 'PUBLISHED' } registerEnumType(PostStatus, { name: 'PostStatus' }); @ObjectType() export class Post { @Field(() => PostStatus) status: PostStatus; } // Union — resolveType tells GraphQL which concrete type an object is export const SearchResult = createUnionType({ name: 'SearchResult', types: () => [User, Post] as const, resolveType(value) { if ('email' in value) return User; if ('title' in value) return Post; return null; }, }); @Query(() => [SearchResult]) search(@Args('query') q: string): Array { return this.searchService.find(q); } @ObjectType() — defines a GraphQL output type returned from queries and mutations. @Field(() => Type) — the arrow function is required for arrays and non-primitive types. registerEnumType() must be called before the enum is referenced in any @Field(). createUnionType() requires a resolveType function — without it GraphQL cannot resolve __typename. nullable: true on @Field() makes the field optional in the schema; arrays use () => [Type].

Difficulty: 5/10

ObjectType, Enum, Union

Use @ObjectType() for output types with @Field() on each property. Register enums with registerEnumType() before using them in @Field(). Create unions with createUnionType() passing a resolveType function that tells GraphQL which concrete type to use at runtime.

ObjectType, enum, and union definitions

Type definition rules:

1
@ObjectType() — defines a GraphQL output type returned from queries and mutations.
2
@Field(() => Type) — the arrow function is required for arrays and non-primitive types.

How do you define a GraphQL object type, enum, and union in code-first NestJS?

Difficulty: 5/10

ObjectType, Enum, Union

Use @ObjectType() for output types with @Field() on each property. Register enums with registerEnumType() before using them in @Field(). Create unions with createUnionType() passing a resolveType function that tells GraphQL which concrete type to use at runtime.

ObjectType, enum, and union definitions

Type definition rules:

1
@ObjectType() — defines a GraphQL output type returned from queries and mutations.
2
@Field(() => Type) — the arrow function is required for arrays and non-primitive types.

How do you define a GraphQL object type, enum, and union in code-first NestJS?

Use @ObjectType() for output types with @Field() on each property. Register enums with registerEnumType() before using them in @Field(). Create unions with createUnionType() passing a resolveType function that tells GraphQL which concrete type to use at runtime.

How do you define a GraphQL object type, enum, and union in code-first NestJS?

Use @ObjectType() for output types with @Field() on each property. Register enums with registerEnumType() before using them in @Field(). Create unions with createUnionType() passing a resolveType function that tells GraphQL which concrete type to use at runtime.

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